1. Technical Field
The present invention is generally directed to a control system for use with cooling systems such as deep fat fryers and, more particularly, to a timed cooking process lock-out for such cooking systems.
2. Description of the Prior Art
Although the invention is discussed below in terms of a deep fat fryer, the present invention is generally applicable to restaurant service equipment, such as pressure and open fryers, which require periodic filtering and other maintenance of a cooking medium.
Typically, deep fat fryers have a temperature probe, a heating element, which may be gas or electric for example, a temperature selector enabling a user to select a desired cooking temperature for a particular food product, product select switches for selecting a particular food product, and a control system which controls the heating element to be operated in different modes corresponding to the different stages of operation of a deep fat fryer. For example, there is often provided a first melt mode wherein solid shortening or liquid shortening below a predetermined temperature is heated at a slow rate, generally by pulsing the heating element until the liquid shortening is heated to a predetermined melt reference temperature. Typically, the heater would then be operated in a second mode wherein the temperature of the shortening is rapidly increased to a selected temperature at which cooking is to occur. As noted, a control system is provided which controls the heating element in these modes. Preferably, a programmable control system is provided which is capable of storing cooking information for a plurality of food products to enable an operator to easily and consistently control the cooking operation. Such a programmable control system is described in commonly assigned, copending application Ser. No. 227,886 incorporated herein in its entirety by the foregoing reference thereto.
An important consideration when using a deep fat fryer for cooking is the proper maintenance of the cooking medium. Specifically, if shortening is used, it is necessary to filter the shortening periodically to maintain cooking quality due to absorption of oils and odor from the cooked food products and degradation of the shortening caused by breakdown thereof due to heat, extended use, amount and type of product breading, and other factors. The number of times a type of food product may be cooked in the same shortening before filtering is required varies from one food product to the next. For example, cooking french fries does not require the shortening to be filtered as often as is required with a breaded product, such as breaded fish. It has been found that cooking breaded fish in a deep fat fryer requires the shortening to be filtered more frequently due to various factors including the oil within the fish and the type of breading used. Other products, such as chicken require a filtration rate somewhere between french fries and fish.
Other procedures are also necessary to properly maintain the cooking medium. For example, after shortening has been filtered a certain number of times, degradation is such that the shortening must be replaced to ensure proper cooking. The filter for filtering the cooking medium must also be replaced periodically.
As noted, filtering may be required after the cooking of a certain number of product loads. Other methods for determining the need for filtering such as exceeding a calculated weighted cycle count based on the number and type of product loads cooked may also be employed. Such a weighted cycle count is described in the aforementioned commonly assigned, copending application. Typically, a filter indicator is activated indicating that filtering should occur. The cooking operation of the fryer may be resumed after the operator has performed the filtering or other maintenance procedure.
A problem arises in that even though a filter indicator is activated, sometimes an operator will ignore the indicator or deactivate it without filtering. This sacrifices cooking and product quality. Prior art methods lockout the cooking process until it is determined that filtering or changing of the cooking medium has occurred. These methods include monitoring the temperature of the temperature probe or monitoring the status of a drain valve switch. The former method is, for example, described in U.S. Pat. No. 4,688,475. However, these methods may be bypassed by an operator who desired to ignore the filtering procedure and continue the cooking process. For example, methods monitoring the status of a temperature probe may be bypassed by dropping the shortening level just far enough to expose the temperature probe, and then cooling the probe with a wet rag. Shortening may then be pumped into the fryer back up to the operating levels. Methods which monitor the status of a drain valve switch may be bypassed by flipping the drain valve handle long enough to signal a filtered condition, even though filtering has not actually occurred.